Edward G. Hohenstein

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Presented here is the optimization and development of a desorption electrospray ionization mass spectrometry (DESI-MS) method for detecting natural products on tissue surfaces. Bromophycolides are algal diterpene-benzoate macrolide natural products that have been shown to inhibit growth of the marine fungal pathogen Lindra thalassiae. As such, they have(More)
Several popular force fields, namely, CHARMM, AMBER, OPLS-AA, and MM3, have been tested for their ability to reproduce highly accurate quantum mechanical potential energy curves for noncovalent interactions in the benzene dimer, the benzene-CH(4) complex, and the benzene-H(2)S complex. All of the force fields are semi-quantitatively correct, but none of(More)
The highly parametrized, empirical exchange-correlation functionals, M05-2X and M06-2X, developed by Zhao and Truhlar have been shown to describe noncovalent interactions better than density functionals which are currently in common use. However, these methods have yet to be fully benchmarked for the types of interactions important in biomolecules. M05-2X(More)
Competitive host-guest chemistry on a desorption electrospray ionization mass spectrometry (DESI MS) platform is presented here as the basis for a rapid and quantitative screening method for assessing the quality of Tamiflu capsules with minimal sample preparation. Oseltamivir, the active ingredient in Tamiflu, is an orally active neuraminidase inhibitor(More)
Noncovalent interactions such as hydrogen bonds, van der Waals forces, and π-π interactions play important roles influencing the structure, stability, and dynamic properties of biomolecules including DNA and RNA base pairs. In an effort to better understand the fundamental physics of hydrogen bonding (H-bonding), we investigate the distance dependence of(More)
Heteroatoms are found in many noncovalent complexes which are of biological importance. The effect of heteroatoms on pi-pi interactions is assessed via highly accurate quantum chemical computations for the two simplest cases of interactions between aromatic molecules containing heteroatoms, namely, benzene-pyridine and pyridine dimer. Benchmark quality(More)
Many approximations have been developed to help deal with the O(N(4)) growth of the electron repulsion integral (ERI) tensor, where N is the number of one-electron basis functions used to represent the electronic wavefunction. Of these, the density fitting (DF) approximation is currently the most widely used despite the fact that it is often incapable of(More)
The S22 test set of interaction energies for small model complexes [Phys. Chem. Chem. Phys. 8, 1985 (2006)] has been very valuable for benchmarking new and existing methods for noncovalent interactions. However, the basis sets utilized to compute the CCSD(T) interaction energies for some of the dimers are insufficient to obtain converged results. Here we(More)
A recent study of substituted face-to-face benzene dimers by Lewis and co-workers [J. Am. Chem. Soc. 2011, 133, 3854-3862] indicated a surprising enhancement of electrostatic interactions for both electron-withdrawing and electron-donating substituents. Here we demonstrate that charge penetration (an attractive electrostatic interaction arising from the(More)
Symmetry-adapted perturbation theory (SAPT) is applied to pairs of hydrogen-bonded nucleobases to obtain the energetic components of base stacking (electrostatic, exchange-repulsion, induction/polarization, and London dispersion interactions) and how they vary as a function of the helical parameters Rise, Twist, and Slide. Computed average values of Rise(More)